The work is expected to proceed in the following directions: 1. Further characterization and explanation of function of thus far unknown iron-sulfur (Fe-S) or Fe-S flavoproteins from mammalian mitochondria. 2. Studies of the function of Fe-S flavoproteins in converting 2 electron into 1 electron transfer, to be carried on mainly with ETF-dehydrogenase and the bacterial enzyme trimethylamine dehydrogenase. 3. Search for "activated" or "primed" forms of cytochrome c oxidase, which show kinetic and EPR characteristics different from the resting enzyme and experiments designed to come to an assignment of some of the high spin forms of the enzyme to either cytochrome a or a3. 4. Further development of the rapid-freeze-quench technique to eliminate artefacts which we have found to occur. Studies on model systems of known kinetic behavior will be required and construction of more efficient mixing chambers and multiple mixing systems. The follow methods will be mainly used: Purification of membrane proteins by detergent solubilization and precipitation and column techniques. Characterization by gel electrophoresis and electrofocussing; by optical and EPR techniques; and by conventional and rapid kinetic methods, particularly freeze-quenching (see 4., above) in combination with EPR and low temperature optical spectroscopy. "Interrelations of Reconstitution Activity, Reactions with Electron Acceptors, and Iron-Sulfur Centers in Succinate Dehydrogenase.", H. Beinert, B.A.C. Ackrell, A. D. Vinogradov, E. B. Kearney, and T. P. Singer, Arch. Biochem. Biophys., (1977), in press. "Kinetics of the Reoxidation of Succinate Dehydrogenase.", B.A.C. Ackrell, E. B. Kearney, C. J. Coles, T. P. Singer, H. Beinert, Y.-P. Wan, and K. Folkers, Arch. Biochem. Biophys., (1977), in press.